There are more than 620 million knees in the United States, and many of them have outlived their warranty. Osteoarthritis of the knees, hips, spine and hands afflicts more than 25,000,000 people, and because obesity is known to increase the risk of arthritis and exacerbate its symptoms, that number is only rising. Pain relief medication, dietary supplements and surgery add up to a multibillion-dollar annual expense. Clearly, modern medicine has not yet defeated osteoarthritis, but understanding which joints are affected and why are good first steps.
Knees
The knee is the joint most commonly affected by osteoarthritis. The Centers for Disease Control and Prevention issue an annual report titled "Health, United States." The 2009 edition, with data tabulated through 2007, reported that 26.5 percent of adults aged 65 years and over had knee joint pain within the past 30 days. Osteoarthritis affected women more than men, and women were 54 percent more likely to have knee replacement surgery than men. Knee replacements last 15 to 20 years.
Hips
The CDC also reported 11.8 percent of adults 65 or older with hip pain. From 1996 to 2006, the number of hip-replacement surgeries among people over the age of 45 years increased more than 30 percent. In the April 2007 issue of the Journal of Bone and Joint Surgery, Dr. Kurtz and co-authors estimated an additional 175 percent increase in hip replacements from 2005 to 2030. While those surgery numbers represent hip replacement for all reasons, osteoarthritis remains the most common reason.
Spine
As with other afflicted joints, osteoarthritis of the spine involves loss of cartilage between bones, chronic inflammation, and pain. Nerves exiting from the spinal column may be unduly subjected to pressure, causing numbness or weakness in arms and legs, in addition to the pain.
Hands
Osteoarthritis of the hands is more strongly inherited than osteoarthritis at other sites. Unlike other types of arthritis, it's rare under the age of 45. Obesity increases the risk of developing osteoarthritis of the hands, suggesting that body fat contributes to whole-body hormonal or inflammatory changes that affect even non-weight-bearing joints. Abnormal growth of new bone tissue in the damaged joints causes the knobby and bent fingers so typical of osteoarthritis of the hands.
Other Sites
While osteoarthritis of the hands, and to a lesser extent of the knees, hips and spine, is in part an inherited condition, osteoarthritis of the shoulder, elbow or foot is more likely to result from physical activity. Wear and tear can cause cumulative damage to a joint. Injury can damage a joint, leading to development of osteoarthritis years later. Interestingly, evidence published by Dr. Eliza Chakravarty in the August 2008 issue of American Journal of Preventive Medicine supports the theory that a repetitive-motion activity such as long-distance running does not increase the risk of osteoarthritis. Contact sports, with the higher risk of injury, may be more likely to lead to osteoarthritis.
References
- Centers for Disease Control and Prevention: Health, United States, 2009
- Journal of Bone and Joint Surgery: Projections of primary and revision hip and knee arthroplasty in the United States from 2005 to 2030
- American Journal of Preventive Medicine: Long distance running and knee osteoarthritis: a prospective study
